The Futility of the Boer's Guerrilla Strategy? 

From a Boer perspective, it can be argued that the guerrilla phase added a heroic chapter to the their history, showing their tenacity and resilience in the face of overwhelming odds. However, all things considered, it was – from a military point of view – a futile and (especially in terms of civilian lives lost) reckless exercise. Especially in the absence of international pressure or support against the aggressive world power of the Brirtish.

Although the guerrilla operations prolonged the conflict, they could not in themselves lead to victory for the Boers. The guerrilla war phase of the war could only create a better platform from which to negotiate favourable terms of peace. 

So, by 1902, the war that was supposed to have been over by Christmas 1899 – and which was supposed to have been a gentleman’s war and a white man’s war – had become a really nasty and bitter conflict, and sometimes – from a British perspective – it nearly spiralled out of control, albeit that, strictly speaking, the eventual outcome was never really in doubt.

While both Roberts and Kitchener initially reviled the guerrillas, Kitchener eventually had to admit that “What are left of the Boers are really fine fellows and when they do fight they do it well.”

Source: Boer Guerrilla and British Counterguerrilla Operations